Retroreflective sheetings have the ability to redirect incident light towards its originating source. This ability has led to the wide-spread use of retroreflective sheetings on a variety of articles including, for example, traffic signs and license plates. There are essentially two types of retroreflective sheeting: beaded sheeting and cube corner sheeting. Beaded sheeting employs a multitude of glass or ceramic microspheres to retroreflect incident light. Cube corner sheeting employs a multitude of rigid, interconnected, cube corner elements to retroreflect incident light.
In cube corner sheeting, a specular reflective coating (e.g., a metallic coating) can be placed on the backside of the cube corner elements to promote retroreflection. Enhanced retroreflection can also be achieved by applying a sealing film or layer to the back side of the cube corner elements either in addition to or in lieu of the metallic coating. The sealing film creates and maintains an air interface at the backside of the cube corner elements and thereby enhances retroreflectivity. Sealing films can also be employed to impart color or protect the cube corner elements from environmental factors. Various sealing films suitable for use with flexible retroreflective sheeting have been described (see, for example, U.S. Pat. No. 5,784,197 (Frey); U.S. Pat. No. 5,691,846 (Benson); U.S. Pat. No. 6,318,867 (Bacon); and U.S. Pat. No. 7,611,251 (Thakkar), all assigned to the present assignee).